The present invention relates generally to gas turbine engines. More particularly, the present invention relates to the mechanical support of a ceramic gas turbine vane ring.
A gas turbine engine consists of an inlet, a compressor, a combustor, a turbine, and an exhaust duct. The compressor draws in ambient air and increases its temperature and pressure. Fuel is added to the compressed air in the combustor to raise gas temperature, thereby imparting energy to the gas stream.
To increase gas turbine engine efficiency, it is desirable to increase turbine inlet temperature. This requires the first stage turbine vanes and rotor blades to be able to withstand the thermal and oxidation conditions of the high temperature combustion gas. While individual ceramic vanes have been the primary focus in the past, ceramic integral vane ring design has gathered momentum for small gas turbines due to advances in ceramic component manufacturing and to requirements for low cost and reliable components.
Although ceramic materials have excellent high temperature strengths, their coefficients of thermal expansion (CTE) are much lower than those of metals, which are commonly used in components that support ceramic vane rings. Additionally, ceramic materials are highly susceptible to localized contact stress due to their brittleness (i.e., inability to deform sufficiently to reduce contact pressure before fracture). Therefore, attachment design of ceramic components requires extra care to take into account these unique characteristics of ceramic materials.
Thus, there exists a need for an assembly capable of supporting a ceramic vane ring while minimizing the possibility of damaging the ceramic vane ring during repeated thermal expansion cycles.